$323 Cheap United flights Philadelphia (PHL) to St. Thomas (STT)

Finding cheap one-way United Airlines flights from PHL to STT from $323 on Expedia is simple --- just filter by "Price (lowest to highest)." Or check out our affordable round-trip fares from $579 for your next break.**These prices were available on Expedia within the past 7 days, for flights departing within the next year. Prices and availability are subject to change. Additional terms apply.

Snagging the best United Airlines deals from PHL to STT often comes down to timing. You can save 17% on international flights when you book 18 to 29 days before takeoff instead of four to five months ahead. To top it off, you can pocket 17% on average by buying your fare on a Sunday rather than a Friday, which is usually the most expensive day to book.* It's a good idea to start searching for flights about one month before you want to travel.*Ideal booking window recommendation is based on average round-trip ticket prices for January through November for 2024. Best day of the week to book recommendation is based on average round-trip ticket prices for January through October 2024. All data sourced from ARC's global airline sales database.

To find the earliest departure from PHL to STT with United Airlines, filter your results by "Morning" and "Early Morning." Booking an early flight generally means cancellations are less likely.**Most reliable time of the day recommendation is based on January through August 2024 flight status data sourced from OAG's global flight data platform.

A rewarding loyalty program and the chance to rack up points through United Mileage Plus are the start of the reasons to leave from PHL to STT with United Airlines. Plus, when you sign up to our One Key™ program, you can receive OneKeyCash™* alongside any airline loyalty program earnings. It's yours to spend on future bookings.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.